Built K24A2 Miata Swap
Posted: Sat May 02, 2026 6:09 pm
I just built a K24A2 for a Miata Race Car that had a Factory K24A2 prior. The build specs are below.
I had this new build dyno tuned and it performed pretty well.
At the road course it runs like a beast but in one part of the track it has an issue.
I brake into a hard right hander, come out on throttle for a brief second, lift into a left hander up hill, then light throttle quickly 0% throttle then back on quickly to 100%.
When I get back on quickly to 100% the engine "falls on its face" and the rpms drop instead of increase.
I can pump the throttle, lift to 0% and get back on, stay steady throttle. Nothing works.
The TPS sensor input is working during this time.
But for about a second the engine just does not respond. Then after that it picks up very abruptly and aggressively! Not smooth!
This happens at almost exactly if not exactly the RPM where the VTEC Window Lower Boundary is set. I am no pro and dont know if this could be the cause. But it certainly seems suspect to me.
I have attached a log that certainly has the issues many time. But it is hard to pinpoint exactly where for me because I don't really know what to look for. And I cant tie the logs to video to see when the issue happens.
I have also attached my calibration file.
Engine build specs:
E85
KPro V4
Factory sleeve bored to 87.5mm
Factory crank 99mm stroke
ARP Main Studs
ARP Head Studs
Brian Crower Rods (BC6052)
CP 12.5:1 Pistons (SC71471XA)
Clevite Main Bearings (.0021" Clearance)
Clevite Rod Bearings (.0025 Clearance)
K20 Ported Oil Pump (4Piston)
Brian Crower Springs (BC0040)
Brian Crower Valves (BC3040 & BC3041)
Brian Crower Valve Locks (BC2940)
Brian Crower Cams (BC0042-2)
TSX Ported Head (4Pistons Pro TSX)
50° VTC Gear (Limited to 40°)
Adjustable Exhaust Cam Gear (Set to 0)
Injector Dynamics Injectors (ID1050XDS)
DeatschWerks Fuel Pump (DW300)
I had this new build dyno tuned and it performed pretty well.
At the road course it runs like a beast but in one part of the track it has an issue.
I brake into a hard right hander, come out on throttle for a brief second, lift into a left hander up hill, then light throttle quickly 0% throttle then back on quickly to 100%.
When I get back on quickly to 100% the engine "falls on its face" and the rpms drop instead of increase.
I can pump the throttle, lift to 0% and get back on, stay steady throttle. Nothing works.
The TPS sensor input is working during this time.
But for about a second the engine just does not respond. Then after that it picks up very abruptly and aggressively! Not smooth!
This happens at almost exactly if not exactly the RPM where the VTEC Window Lower Boundary is set. I am no pro and dont know if this could be the cause. But it certainly seems suspect to me.
I have attached a log that certainly has the issues many time. But it is hard to pinpoint exactly where for me because I don't really know what to look for. And I cant tie the logs to video to see when the issue happens.
I have also attached my calibration file.
Engine build specs:
E85
KPro V4
Factory sleeve bored to 87.5mm
Factory crank 99mm stroke
ARP Main Studs
ARP Head Studs
Brian Crower Rods (BC6052)
CP 12.5:1 Pistons (SC71471XA)
Clevite Main Bearings (.0021" Clearance)
Clevite Rod Bearings (.0025 Clearance)
K20 Ported Oil Pump (4Piston)
Brian Crower Springs (BC0040)
Brian Crower Valves (BC3040 & BC3041)
Brian Crower Valve Locks (BC2940)
Brian Crower Cams (BC0042-2)
TSX Ported Head (4Pistons Pro TSX)
50° VTC Gear (Limited to 40°)
Adjustable Exhaust Cam Gear (Set to 0)
Injector Dynamics Injectors (ID1050XDS)
DeatschWerks Fuel Pump (DW300)